There are in fact several N&W J class running around. 600, 608, 611, & 612 all exist in my Rail Yard. I know one of them was the result of the "Lionel Collection" that was done years back, but I don't remember who did that one. A quick search of my CM yields 2 done by one "Newyorkcentral", numbers 608 (<kuid:339906:101091>) & 611 (<kuid2:339906:100112:1>), Error Free, though with a couple warnings, Build 61388. I also have # 600 (2 Listings;<kuid:96914:6051> & <kuid:96914:6050>), done by Ben Neal (Bdaneal), but they're listed as Obsolete, though I think they do Load up in the sim. The last one I can't seem to find (Should be 612), and I'm pretty sure it won't load up in the sim either. I think the last one is probably the Lionel Collection one, but I'm not sure.
Regardless, yes, K&L's new N&W Water Tender looks great behind the ones that I have that work!
Good Luck!
Falcus